Trichophyton spp- An Overview


Trichophyton is a genus of fungi that belongs to the family Arthrodermataceae and the order Onygenales. It includes about 20 species that can infect the skin, hair and nails of humans and other animals, causing various types of dermatophytosis or ringworm infections . Trichophyton species can be classified into three groups based on their habitat preference: anthropophilic (human-associated), zoophilic (animal-associated) and geophilic (soil-associated) . Some of the most common and clinically important species are:

  • Trichophyton rubrum: an anthropophilic fungus that causes chronic infections of the feet, skin and nails, especially in tropical regions .
  • Trichophyton mentagrophytes: a zoophilic fungus that affects various animals, such as rodents, cats, horses and rabbits, and can also cause ringworm of the scalp, skin and nails in humans, mainly in rural areas .
  • Trichophyton tonsurans: an anthropophilic fungus that causes tinea capitis (scalp ringworm) and tinea corporis (body ringworm) in humans, especially children .
  • Trichophyton verrucosum: a zoophilic fungus that causes ringworm in cattle and other livestock, and can also infect humans through contact with animals or contaminated objects .
  • Trichophyton violaceum: an anthropophilic fungus that causes tinea capitis and tinea corporis in humans, especially in Africa, Asia and Europe .

Trichophyton fungi are molds that produce both macroconidia (large spores) and microconidia (small spores) on their hyphae (filaments). The shape, size and arrangement of these spores vary depending on the species and the culture conditions . Trichophyton fungi can be identified by microscopic examination of skin scrapings, nail clippings or hair plucks treated with potassium hydroxide (KOH) or calcofluor white, which dissolve the keratin and reveal the fungal elements . They can also be cultured on selective media, such as Sabouraud dextrose agar (SDA) with cycloheximide and chloramphenicol, which inhibit the growth of other molds and bacteria . The colony morphology, pigmentation and microscopic features of Trichophyton fungi can help differentiate them from other dermatophytes or non-dermatophytic molds .

Trichophyton fungi cause dermatophytosis by invading the keratinized tissues of the skin, hair and nails. They secrete enzymes that degrade keratin and allow them to penetrate deeper into the tissue. They also elicit an inflammatory response from the host immune system, which results in symptoms such as itching, scaling, redness, vesicles, pustules, crusts and alopecia . The clinical manifestations of dermatophytosis depend on the site of infection, the species of Trichophyton involved and the host factors. Some of the common types of dermatophytosis caused by Trichophyton are:

  • Tinea pedis (athlete`s foot): a fungal infection of the interdigital spaces or the soles of the feet caused by T. rubrum or T. mentagrophytes .
  • Tinea corporis (ringworm): a fungal infection of the non-hairy skin of the trunk or limbs caused by various Trichophyton species .
  • Tinea capitis (scalp ringworm): a fungal infection of the scalp hair caused by T. tonsurans, T. mentagrophytes or T. violaceum .
  • Tinea barbae (barber`s itch): a fungal infection of the beard area caused by T. verrucosum or T. mentagrophytes .
  • Tinea unguium (onychomycosis): a fungal infection of the nails caused by T. rubrum or T. mentagrophytes .

The treatment of dermatophytosis caused by Trichophyton involves the use of topical or oral antifungal agents, depending on the severity and extent of the infection. Some of the commonly used antifungal drugs are azoles (e.g. ketoconazole, itraconazole, fluconazole), allylamines (e.g. terbinafine, naftifine), griseofulvin and ciclopirox . The prevention and control of Trichophyton infections require the maintenance of good hygiene, the avoidance of contact with infected individuals or animals, the disinfection of contaminated objects and the prompt diagnosis and treatment of cases .